Skip stitch mechanism for sewing machines

ABSTRACT

A sewing machine needle reciprocating mechanism is disclosed including clutch mechanism for releasing the endwise reciprocatory drive for the needle bar intentionally to provide for skipped stitches as for basting or the like, and also to provide for an automatic release of the needle bar drive to prevent needle breakage in case the needle should strike an impenetrable object such as a button or the like.

United States Patent 91 Graham SKIP STITCH MECHANISM FOR SEWING MACHINES[75] Inventor: Thomas G. Graham, Point Pleasant Beach, NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Feb. 22, 1972 [21] App1.No.: 228,026

52 user ..112/221 [51] 1m.c|......, ..D05b69/36 [58] Field of Search..l12/221,220,219 R,

[56] References Cited UNITED STATES PATENTS 3,471,325 10/1969 Berube 112/221 51 Apr. 17, 1973 Scheibel .11 12/221 Basso ..1 12/221 PrimaryExaminer-H. Hampton-Hunter Attorney-Marshall J. Breen et a1.

57 ABSTRACT A sewing machine needle reciprocating mechanism is disclosedincluding clutch mechanism for releasing the endwise reciprocatory drivefor the needle bar intentionally to provide for skipped stitches as forbasting or the like, and also to provide for an automatic release of theneedle bar drive to prevent needle breakage in case the needle shouldstrike an impenetrable object such as a button or the like.

' 1 Claim, 2 Drawing Figures PAIENIEU APR 1 71973 gm w SKIP STITCHMECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION Needle barmechanisms are known in the prior art including releasable clutch meanswhich may be influenced selectively to provide for skipped stitches.These known skip stitch mechanisms require mechanism for actuating theclutch means and do not serve as safety releases to protect the sewingmachine operator in case the needle should strike an impenetrableobject.

Safety clutches are known in the sewing machine art for interrupting theneedle bar drive in the event that the needle strikes animpenetrable-object. These safety release needle bar clutches had notheretofore been organized so as to be selectively operable and,therefore, they have not been heretofore usable to provide bastingstitches or other operations requiring predetermined interruption ofneedle bar reciprocation.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention toprovide a sewing machine needle bar mechanism including a singleseparable driving connection between the needle bar and the needlebarreciprocating mechanism, which separable driving connection serves as asafety device automatically opening when the needle bar meets excessiveresistance to endwise movement, together with a means for separatingsaid driving connection at will so that predetermined interruption ofneedle bar reciprocation may be attained.

DESCRIPTION OF THE DRAWING With the above and additional objects andadvantages in view as will hereinafter appear, this invention isillustrated in the accompanying drawing of a preferred embodiment inwhich:

FIG. 1 represents a side elevational view of the head portion of asewing machine with the sewing machine frame partly broken away toexpose this invention applied thereto, and

FIG. 2 is an enlarged cross sectional view of the separable drivingconnection between the needle bar and the actuating mechanism therefor,taken substantially along line 2-2 of FIG. I, but shown with the drivingconnection interrupted.

Referring to the drawing, 11 indicates the bracket arm head portion of asewing machine frame formed with a web 12 in which a main drive shaft 13is jour naled. A counterbalance 14 fast on the main drive shaft 13carries a crank pin 15 which constitutes the operating mechanism forimparting endwise reciprocatory movement to a needle bar 16 journalcdfor endwise reciprocatory movement in bearings 17 and 18 in the bracketarm head 11. At the lower extremity the needle bar carries a needleclamp 19 by which a conventional sewing machine needle 20 may be securedthereto.

The driving connection between the crank pin 15 and the needle bar 16comprises a drive link 21 formed at one extremity with a boss 22embracing the crank pin 15 and formed at the opposite extremity with aboss 23 which embraces a drive stud 24 which projects laterally from ablock 25 slidable lengthwise along the needle bar 16. The block 25 isformed with a transverse 0 and the clutch pin may also be formed with apilot pin 36 at the free extremity. The clutch pin is urged toward theright as viewed in FIG. 2 in a position maintaining the pilot pin 36 inan elongate slot 40 in the needle bar accommodate the pilot pin 36, andat the upper extremity the elongate slot 40 joins a transverse notch 41shaped to accommodate the free extremity of the clutch pin 31.

When the clutch pin 31 is seated in the transverse notch 41 of theneedle bar, the driving connection for imparting endwise reciprocatorymovement to the needle bar will be effective. If an abnormal resistanceto endwise reciprocation of the needle bar is encountered, the clutchpin 31 will be forced out of the transverse notch 41 and the pilot pin36 will be shifted relatively to the needle bar and along the elongateslot 40. The needle bar 16 will thus be arrested in its endwisereciprocation and needle breakage and the consequent risk of injury tothe work or to the sewing machine operator will be averted. The slot 40and the pilot pin 36 will prevent the needle bar from turning whether ornot the driving connection is effective.

A cushion spring 50 is provided on the bracket arm head portion 11 abovethe needle bar 16 for engagement of the needle bar when the drivingconnection is interrupted. Because of the cushion spring the needle bar16 will be constrained substantially in its uppermost position ofreciprocation and the separable driving connection will bere-established on the next upstroke of the driving mechanism.

For intentionally interrupting the drive connection for endwisereciprocation of the needle bar, a pawl 60 is pivoted to a support lug61 on the needle bar 16 and a spring 62 carried by the pawl abuts theneedle bar to urge the pawl outwardly from the needle bar. Carried as bya fastening screw 63 on the bracket arm head portion 11 of the sewingmachine frame is a leaf spring 64 to which an abutment block 65 isattached as by a screw 66. The leaf spring 64 may be oriented adjacentto or projecting through an aperture 67 in the bracket arm head portion11 and carries in the vicinity of this aperture a push button 68.

If it is desired to interrupt the needle bar reciprocation purposely asto perform basting stitches or for any other reason, the operator needssimply depress the push button 68 to shift the abutment block 65 intothe path of the pawl 60 on the needle bar. On the ensuing rise of theneedle bar the latch pawl 60 will deflect past the abutment block 65 andthe spring 62 will force the pawl outwardly in a position overlying theabutment block. When the needle bar begins a downwardwork penetratingstroke of reciprocation, the pawl 60 in engagement with the abutmentblock 65 will provide abnormal restraint to endwise reciprocatorymovement and the clutch pin 31 will be forced out of the transversenotch 41 in the needle bar thus to interrupt the driving connection ofthe needle bar with the needle reciprocating mechanism. Because of thepawl arrangement such needle bar interruption cannot occur during thewithdrawal stroke of the needle bar from the work but only upon theneedle penetrating stroke. When the push button 68 is released, theneedle bar on the next upstroke of the drive mechanism will re-establishdriving connection therewith.

Having set forth the nature of this invention, what is claimed hereinis:

l. A skip stitch mechanism in a sewing machine having a frame, a needlecarrying bar supported in said frame for endwise reciprocation to impartwork penetrating and withdrawal strokes to a needle carried thereby,actuating mechanism carried in said frame for imparting endwisereciprocatory movement to said needle bar, said skip stitch mechanismcomprising in combination a driving connection between said actuatingmechanism and said needle bar which is automatically separable inresponse to application of a preselected level of resistance to endwisereciprocation of said needle bar, and blocking means between said frameand said needle bar selectively effective to prevent penetrating strokesof said needle bar.

1. A skip stitch mechanism in a sewing machine having a frame, a needlecarrying bar supported in said frame for endwise reciprocation to impartwork penetrating and withdrawal strokes to a needle carried thereby,actuating mechanism carried in said frame for imparting endwiserEciprocatory movement to said needle bar, said skip stitch mechanismcomprising in combination a driving connection between said actuatingmechanism and said needle bar which is automatically separable inresponse to application of a preselected level of resistance to endwisereciprocation of said needle bar, and blocking means between said frameand said needle bar selectively effective to prevent penetrating strokesof said needle bar.